The disclosure relates to a semiconductor storage device, and can be particularly applied to a content addressable memory that can be incorporated into a semiconductor device and a semiconductor device including a content addressable memory.
A data word (entry) matching a search word (search data) is searched for among those stored in a semiconductor storage device called an associative memory or a CAM (Content Addressable Memory). In the case where the word data matching the search word can be found, the address thereof is output.
As the CAM, there are a BCAM (Binary CAM) and a TCAM (Ternary CAM). Each memory cell of the BCAM stores information of either “0” or “1”. On the other hand, each memory cell of the TCAM can store information of not only “0” and “1” but also “Don't Care”. The “Don't Care” indicates that either of “0” and “1” may be stored.
In recent years, a TCAM device using the TCAM has been widely used for address search and access control in a router for a network such as the Internet.
A second embodiment of Japanese Unexamined Patent Application Publication No. 2007-19166 discloses a technique in which two memory cells share a search line.